Bystanders are often the first people on the scene of a disaster, even before trained emergency responders. A tourniquet is an effective way to stop uncontrolled bleeding from an arm or leg after an explosion, gunshot or other trauma.

Anyone can learn to use a tourniquet, and everyone should have a commercially-made tourniquet in their first aid kit. Two is even better. When you purchase a tourniquet, look for one with a wide band and a windlass (handle) that can be twisted to tighten the tourniquet. Two good tourniquets widely available online are the Combat Application Tourniquet (CAT) and the SOF Tactical Tourniquet.

Using a tourniquet is a skill that can be mastered with a little training and practice like the Heimlich maneuver or CPR. Tourniquets are only to be used on arms or legs. In my experience, a properly applied tourniquet can save lives.

I recommend watching my video demonstration, above.

A good tourniquet has a wide band and a handle, called a windlass, for tightening.

Tourniquet Step-By-Step

If you see an injured person, first call 911. Safety comes first. Look around to see if you are in a safe location and if not, move yourself and the injured person to safety.

Tourniquets are used only on arms or legs to stop uncontrolled bleeding.

First, to get in position, kneel next to the wounded person and unfold the tourniquet.

Wrap the tourniquet around the arm or leg above the bleeding and pass the free end of the tourniquet through the buckle of the opposite end.

Pre-tighten the tourniquet by pulling on the free end of the tourniquet strap through the buckle at the opposite end. Make it tight enough that you cannot place a finger between the tourniquet and the patient’s skin.

Twist the windlass (handle) as many as three times or until the bleeding stops. Secure the windlass in place using the windlass locking clip. You can tighten the tourniquet by twisting the windlass in either direction.

Inspect the wound to make sure there is no bleeding and feel for a pulse at the wrist or ankle. You should feel no pulse.

If the bleeding continues, and you have a second tourniquet, place it around the limb above the first and follow the instructions above.

Write the time on the tourniquet so that the trained medical professionals at the hospital will know how long it has been in place.

Once the tourniquet is in place, do not move or adjust it. Leave the tourniquet in place until the patient can be evaluated at a hospital

David R. King, MD, CCC-SLP, is a trauma and acute care surgeon at the MGH Trauma Center. He is also an attending physician in the Surgical Intensive Care Unit. As a U.S. Army Surgeon, Dr. King has deployed to both Afghanistan and Iraq. He completed running the 2013 Boston Marathon just before the bombings and then worked around the clock in the MGH operating room to help save the lives of victims.